Fluid powered gun for setting fasteners



June 19, 1962 w- R. SIMMONS FLUID POWERED GUN FOR SETTING FASTENERS 2 Sheets-Shea?l 1 Filed July 14, l958` u m? W5 w m M@ m M `une 19, 1962 W. R. SIMMONS FLUID POWERED GUN FOR SETTING FASTENERS 2 Sheets-Sheet 2 Filed July 14, 1958 INVENTOR. WAM 75e f@ MMoA/s BY zmr/fee/M United States Patent O 3,039,270 FLUID POWERED GUN FR SETTING FASTENERS Walter R. Simmons, Baena Park, Calif., assigner to Townsend Company, a corporation of Pennsylvania Filed .luly 14, 195g, Ser. No. 748,394 6 Claims. (Cl. 60-54.5)

This invention is concerned with tools for setting certain types of fasteners, such as lock bolts and the like. The invention deals more particularly with a liuid powered gun for operating the so-called pulling and swaging heads which are used to set such fasteners.

Fasteners of the type with which this invention is concerned consist, briefly, of an inner stem and an outer collar slideable on the stem. The fasteners are set in the known way by holding the collar stationary and drawing the stern through the collar to firmly clamp the workpieces being joined between the collar and a head on the stem. The collar is then swaged on the stern.

This pulling and swaging operation is performed by a setting tool commonly referred to as a pulling land swaging head. Briefly stated, such a head is equipped with an inner collet or drawbolt which is arranged to be iixed to the fastener stern and an outer slideable sleeve which is engageable with the fastener collar.

In operation, the draw bolt is pulled into the sleeve while the collar is held stationary by the sleeve to effect drawing of the fastener stem through the collar in the manner mentioned. The sleeve embodies a swaging anvil at its outer end which is forced over the collar to swage the fastener collar on its stem.

A broad object of this invention is the provision of a iluid powered gun for operating a fastener setting tool of the character described.

A more specific object of the invention is the provision of a gun of the character described which is powered by both pneumatic and hydraulic pressure.

Another object is the provision of a fluid powered gun of the character described which employs a pneumatichydraulic booster action for increasing the operating force of the gun.

Yet another object is the provision of a fluid powered gun for a fastening setting tool of the character described embodying a novel return piston arrangement for developing the positive operating force necessary to release the swaging anvil of the tool from the swaged collar of the fastener.

A further object is the provision of a fluid powered gun of the character described having an open hydraulic system which is automatically replenished with hydraulic fluid from a self-contained fluid reservoir after each operating cycle of the gun.

Other objects, advantages and features of the invention will become apparent as the description proceeds.

Briefly, these objects are attained by the provision of a gun equipped with a pneumatically powered, hydraulic booster or power piston. Hydraulic iiuid displaced from the piston cylinder during one stroke of the piston operates a head piston in one direction. This head piston is arranged for connection to the drawbolt of the setting tool and is movable in a head having means for connection to the sleeve of the setting tool.

Movement of the head piston in the mentioned direction is utilized to set and swage the fastener. During the return stroke of the head piston, the -swaging anvil of the setting tool is released from the fastener collar and the draw bolt of the setting tool is returned to normal position.

The gun embodies a return piston, operated by the power piston near the end of its return stroke, for feeding hydraulic uid to the head piston for the return stroke of the latter. This arrangement yields a sufficient,

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positive hydraulic force on ythe head piston during its return -stroke to release the swaging anvil of the setting tool.

The arrangement of the return piston is unique and permits an open hydraulic system which is automatically replenished after each cycle of the gun.

A better understanding of .the invention may be had from the following detailed description taken in connection with the annexed drawings, wherein:

FiG. l is a longitudinal section through the present gun, the parts of the latter being shown in their normal inoperative positions;

FIG. la is a section taken along line lez-1a of FIG. 1;

FIG. 2 is a section taken along line 2-2 of FIG. 1;

FIG. 3 is a section taken along line 3-3 of FIG. 1; and

FIG. 4 is a partial view similar to FIG. 3 illustrating A certain parts of the latter ligure in a different position of operation.

Referring now to these drawings, the present fluid powered gun will be seen to comprise la hollow, fluid-tight body or handle 20. The lower end of this handle is cylindrically enlarged to form a main pneumatic cylinder 22. A main piston 24 moves in this cylinder.

During operation of the gun, pressure air for causing the down stroke of the piston 24 enters the upper end of the cylinder 22 through a passage 26. Pressure air for causing the up or return stroke of the piston to its normal inoperative position of FIG. l enters the lower end of the cylinder through a passage 28.

Passages 26 and 28 communicate, respectively, with a pair of spaced, rectangular openings 30 and 32 in the handle above the cylinder 22. These rectangular openings, as well as a third rectangular opening 34, located between the openings 30 and 32, open through a side face 36 of the handle.

Overlying the face 36 is a valve plate 38. A pair of outer and inner seat gaskets 40 and 42 are placed on the outside of this plate -as well as between the latter and face 36. Valve plate 38 and the `gaskets 40 and 42 have three rectangular openings 30', 32 and 34' aligned, respectively, with the openings 30, 32 and 34.

Fixed by bolts (not shown) -to the handle 20, and lagainst the outer gasket 40, isa v-alve block l46. This valve block has a valve chamber 48 registering with the valve plate openings 30', 32 and 34. Located in this chamber is a hollow slide valve 50.

Slide valve 50 has a yoke S2 which engages between :a pair `of shoulders 54 on the shaft 56 of a control piston 58. The slide valve is urged ilat against the valve plate 38 by a compression spring 60.

The control piston 5S is movable between its normal position of FIG. 3 and its limit position of FIG. 4 to shift the slide valve 50 between its feed stroke position of FIG. 4 and its return stroke position of FIG. 3. In its feed stroke position, the slide valve uncovers the valve plate opening 30', communicating with lair passage 26, and cornmunioates valve plate opening 32', leading to air passage 28, with valve plate opening 34.

This latter opening 34 connects with a passage 62 which vents to atmosphere through muffler packing 64. Mufer packing 64 is retained in -a recess 66 by la permeable cover 68 held on by screws, as shown.

In its return stroke position of FIG. 3, the slide valve 50 uncovers the valve plate opening 32 and communioates the vent or exhaust passage 62 to the v-alve plate opening Sli.

Indicated at 7 0 is `a swivelly mounted, ai-r hose coupling through which pressure air may be admitted to the valve chamber 48 via the valve block passages illustrated. In the feed stroke position of the slide valve 50, this pressure air enters the upper end of the pneumatic cylinder 3 22, through the passage 26, to move the pneumatic or main piston 24 downwardly. Air from below the piston exhausts to atmosphere through passage 28, slide valve Si) and exhaust passage 62.

"1n the return stroke position of the slide valve, pressure air in valve chamber 48 enters the lower end of the pneumatic cylinder 22, through passage 2S, to move the piston 24- to its norma upper position of FIG. l. Air `above the piston exhausts to atmosphere through passage 26, slide valve 50 and exhaust passage 62.

The shaft or rod 56 of the control piston 5S has a somewhat loose sliding t in a bore in an internal wall 72 of the valve block which separates the value chamber 4S from the cylinder 74 for the control piston. Air may, therefore, leak from the valve chamber to the cylinder 74, `at the right side of the control piston, through the restricted clearance space or passage 75 between the piston rod 56 and wall 72.

The cylinder 74, to the left of the control piston, communicates to the valve chamber 48 through a passage 76 in the piston rod 56. A spring 78 -biases `the control piston to the left to its normal position of FIG. 3.

Opening to the cylinder '74 behind, that is, to the fright of the control piston '74, is la vent passage 30. This passage extends upwardly through the handle 20 to a manu-al control valve 82.

Control valve 82 includes a stem 84 having a loose sliding fit in a bore 86 in the handle. An `air leakage space 87, therefore, exists between the stem S4 `and wall of the bore 86. This space is larger than the leakage space 75 past the control piston rod 56. The inner end of the stem 84, which iis located in the vent passage Si), mounts an O-ring seal 86. This seal is normally held `against a seat S8, `to `close said leakage space 85, by air pressure in the vent passage 80.

With lthe control valve 82 closed, air pressure on vopposite sides of the control piston S 4is equalized. The control piston is, therefore, moved -to its normal position of FIG. 3 by its spring '7%. The pneumatic piston 24 is thus held in its normal upper position of FG. l.

When the control valve 82 is depressed, ai-r leaks from behind the control piston 58 to atmosphere through vent passage 80 and leakage space 87. Since, Ias mentioned, the leakage space S7 is larger than the leakage space 75 past the control piston rod 56, the pressure behind the control piston 5S drops. High pressure lair still `acts on the front or left side of the control piston, however, by virture of the passage 76.

The control piston is thereby shifted to the right to its limit position of FIG. 3. Pressure air is now :admitted 'to the upper end `of the pneumatic cylinder 22 to move the pneumatic piston 24 in its feed stroke. When the control valve is `again released, the control piston returns to its normal position Iand the pneumatic piston is moved in its return stroke to its normal upper position.

Secured to the pneumatic piston 24 and extending upwardly therefrom through the handle 20 is ya piston rod 39 carrying a floating power piston 90. Power piston 9h moves in a cylinder sleeve 92 which is formed separately from the handle. The upper end of the cylinder sleeve 92 is open and terminates below the upper end of the handle 20.

Adjacent its lower end, the cylinder sleeve 92 has a close sliding tit in :a bore 94 formed in yan internal transverse wall 96 of the handle 20. Bore 94 is counterbored at 98 and opens downwardly into the pneumatic cylinder 22. The lower end of the cylinder sleeve 92 is externally formed with a relatively Ithick annular shoulder 1&1@ which has a close sliding fit `in the counterbore 98. This shoulder is sealed to the wall of the bore 9S by the O-rings illustrated. The lower end of the cylinder sleeve 92 is open.

Threaded in the lower end of the counterbore 98, so as to close the latter, is a packing plug 162. This plug abuts the lower end of the cylinder sleeve 92 and holds the annular shoulder 160 on the sleeve tightly up aga'mst the internal handle wall 96. O-ring seals for this plug are placed `as shown.

Packing plug 102 has a central axial bore slidably receiving the power piston rod S9. This piston rod is slideably sealed to the packing plug 102 by packers :or O-ring seals 1&4.

The floating power piston is located between `a lower retaining ring 196 `and an upper annular shoulder 1% on the piston rod 89. The :axial spacing between the retaining ring 166 and the shoulder 16S is somewhat greater than the `axial dimension of the power piston 90. The latter is, therefore, capable of limited axial movement on the piston rod 89.

The inner cylindric wall of the power piston is spaced from the piston rod to provide a fluid passage 1,10. During the hrst part of the down stroke of the piston rod 39 from its normal upper position, illustrated, the floating piston 90 remains stationary until la conical valve face 112 on the lower side of the piston -rod shoulder 108 engages a conical valve seat 114 on the upper side of the floating piston. This engagement of the valve face and valve seat closes the iluid passage and also connects the floating .piston to the piston rod 89 for downward movement with the latter.

During operation of the gun, the annular space 116 between the power piston cylinder 92 `and the power piston rod 89 is filled with hydraulic fluid. When the control valve `82 is depressed to cause a down stroke of the pneumatic piston 24 in its cylinder 22, the power piston 9i) is moved downwardly in its cylinder 92. As just mentioned, the iiuid passage 110 to the power piston is then closed. The hydraulic iluid displaced from the space i116 during this down stroke ot' the power piston `hows through radial ports 118 at the lower end of the cylinder 92 into -a passage 120 in the handle 20.

This latter passage extend-s upwardly through the handle and opens into the inner or right-hand end of a cylinder i122 in an upper body or head 124. As shown, this head 124 is formed separately from the remainder of the handle 20. rllhe head is held on the handle by attaching screws 126. An O-ring seal 128 encircles the hydraulic fluid passage at the interface between the head 124 and handle 20 to prevent leakage of hydraulic uid at this point.

It will be observed that the head 124 closes the open upper end of a chamber 130 in the handle 20. The annular space 132 between the wall of the chamber 11i@` and the outer wall of the sleeve 92 forms a hydraulic iluid reservoir, as will be shortly further explained.

Fitted in the rear or left-hand end of the head cylinder 122, and retained on the head by the screws illustrated, is a head cap 134. This head cap includes the sleeve portion 136 which projects a. distance into the head cylinder and forms a stop for a head or work piston 138 which is movable in the cylinder 122.

Extending from the rear or left-hand side of the head piston 138 is a sleeve 140. This sleeve has a close sliding tit in the bore 142 of the head cap 134. The head cap is sealed to the piston sleeve yand wall of the head cylinder i122 by the O-rings illustrated.

Extending from the forward `or right-hand side of the head piston 138 is la piston rod 144. This piston rod has a sliding ft in a reduced axial bore 146 in an opening through the -forward side of the head 124. The piston rod 144 is sealed to the bead by the O-rings shown. The forward end of the piston rod 144 is slightly reduced and externally threaded at 14S to form a rod coupling for connection to the collet or draw bolt D of a pulling head H of the character preliminarily mentioned. The forward or right-hand end of the head bore 146 is counterbored and internally threaded at I'150 for threadedly receiving the reduced rear end of a head extension 152. The forward end of this head extension is axially slotted 'at 154 and annuliarly grooved at 156 to form a sleeve coupling for receiving projecting lugs L on the sleeve S of the pulling head. This sleeve is locked to the bead extension `152 by inserting the lugs on the sleeve S into the slots 154 and then rotating the lugs into the annular grooves 156.

Rotatable and axially movable on the head extension 152 is a locking sleeve 158. This locking sleeve is biased rearwardly to the position illustrated by a coil spring 160. Coil spring 160 acts between an annular shoulder 162 on the head extension 152 and a lock ring 164 aiiiXed in the rear end of the locking sleeve. Rearward movement of the locking sleeve is limited Eby a stop ring 166 clamped between the rear side of the head extension 'and the forward side of the head 124.

Locking sleeve 158 is provided with inwardly extending fingers 170 which project through the slots 154.

When assembling a pulling head on tbe 1gun,'the locking sleeve `158 is pushed forwardly to disengage the locking sleeve fingers 170 from the `slots 154 and then rotated to misalign the flanges and slots. The rear end of the drawbolt D is then threaded on the forward end of the power piston rod `144, as shown. Next the sleeve S of the pulling head is slipped over the drawbolt and its lugs and rotated into the annular grooves 156 in the head extension 152 in the manner described above.

After the lugs have been thus engaged in the annular grooves on the head extension, the fingers 170 on the locking sleeve 158 are reengaged in the head extension slots 154. In this position, the locking sleeve flanges prevent rotation of the pulling head sleeve lugs into the eX- tension slots 154 Iand hence act to lock the pulling head -sleeve on the head extension.

As previously mentioned, the hydraulic fiuid displaced by the power piston 90 during its down stroke flows through the passage 120 intothe forward end ofthe head cylinder A122. The pressure of this fluid acts to move the head piston 138 rearwardly until it engages the forward end of the head cap sleeve 136. During this rearward movement of the head piston, the draw bolt of the pulling head is pulled rearwardly through the sleeve of the pulling head to effect setting land swaging of a `fastener in the man-ner preliminarily mentioned. The

outer end of the fastener stem is normally severed during this setting operation and ejected rearwardly through an axial passage 172 in the head piston rod 144.

This passage 172 opens intoa passage 174 in a de- -fiector fitting 176. This deector fitting is held in the rear sleeve 140 of the head piston `138 by a retaining ring 178. A coil spring 180 acting between the head piston 138 and an annular shoulder 182 on lthe outside of the deflector fitting serves to hold the latter tight against the retaining ring 178 so as to prevent rattling of the fitting.

The deflector fitting passage 174 opens through a headed nipple 184 on the rear end of the defiector fitting. A downwardly opening, iiexible defiector 186 is afiixed to this nipple. This defiector acts to downwardly deiiect any severed fastener stems which are ejected rearwardly through the passages 172 and 174 during setting of a fastener.

Generally indicated at 188 is `a return piston assembly which supplies hydraulic fluid to the rear side of the head piston y138 for returning the latter from its rear limiting position against the head cap sleeve 136 to its normal forward position of FIG. 1. This return piston assembly comprises an open-ended cylinder sleeve 190. The upper end of sleeve 190 is threaded in a downwardly opening bore 192 in the under face of the head 124-. A port 194 communicates the upper end of cylinder 190 with the head Engaging between the upper face of this shoulder and the head 124 is a coil spring 202. This spring biases the return piston 196 in a downward direction. Downward movement of the return piston is limited by a stop ring 204 affixed in the lower end of the return cylinder 190.

During the latter pant of the upward, or return stroke of the pneumatic piston 24 and the power piston 90, the return piston 196 is moved upwardly, against the action of spring 202, to its upper position of FIG. 1 by engagement of the upper annular face 206, on the power piston rod shoulder 108, with the lower annular face 208` on the return piston shoulder 200. Annul-ar faces 206 and 208 form sealing faces which, when engaged, prevent hydraulic fiuid trapped within and above the return piston from leaking out through the lower end of the latter during the upstroke of the return piston. The upper end of the power piston rod 89 has a cylindrical guide portion 210 which is slideably engageable in the axial opening or passage 211 of the return piston shoulder 200.

A sleeve 212 is tightly fitted on lthe outside of `the return piston sleeve 198 and extends below the lower end of the latter, as shown. In the upper normal positions of the parts, the lower end of this sleeve 212 terminates just above the power piston,

During the downward or pumping stroke of the power piston 90 to produce `a left-hand or pulling stroke of the head or work piston 138, the return piston 196 moves downwardly, under the action of the spring 202, to its lower limiting position in contact with the stop ring 204. The rate of downward movement o-f the return piston 196 is limited by the rate of flow of uid upward through passage 211. Thus piston rod 89 moves down faster than return piston 196 and permits separation of sealing faces 206 and 208, Piston rod valve faces 112 and 114 engage during this down stroke of the piston rod 89 so that fluid in chamber .116 is forced into cylinder 122 at the right side of piston 138, as discussed earlier.

During the left-hand pulling stroke of the head piston 138, hydraulic fluid is displaced from the head cylinder 122 into the upper end of the return cylinder 190 through 'the por-t 194. Additional hydraulic fluid ows from the reservoir 132 to the interior of the return piston through the passage 211. Subsequent engagement of the sealing faces 206 and 208 during the following upward return stroke of the power piston closes the passage 211 so that lthe fiuid in and above the return piston 196 is trapped. As the return piston is moved upwardly by the power piston rod 88, near the end of the return stroke of the latter, this trapped uid is forced into the head cylinder 122 to move the head piston 138 in its right-hand return stroke.

The return piston arrangement described above is designed to produce `a sufiicient right-hand force on the head piston 138 to effect disengagement of the swaging -anvil of the pulling head from the swaged collar of the fastener and at `the same time make it possible to have an open hydraulic system which can be continuously replenished after each cycle of the gun. in order to make this action of the return piston quite positive, the latter is designed to displace a greater volume of hydraulic fluid into the head cylinder than the head cylinder space to the -left of the head piston.

Accordingly, the head piston 138 reaches the right-hand limit of its return stroke (FIG. l) prior to the return piston reaching the upper limit of its pumping stroke. The eXcess hydraulic iiuid `displaced by the return piston during the remaining portion of its pumping stroke flows through a by-pass passage 214 (FIG. 2), containing a one-way check and relief valve 216, to the hydraulic fluid reservoir 132. This valve includes a spring, as shown, which retains the valve closed until the pressure in the rear end of the head cylinder attains a predetermined value.

Operation YIn operation of the gun described above, the swivel fitting 70 is connected to an air supply hose 218, leading to a supply of pressure air (not shown). Air entering the gun through the fitting 70 leads into the right-hand end of the control piston cylinder 74 and the contro-l valve passage 8G through the passage or clearance space 75 between the control piston rod 56 and the wall of its bore. Pressure air also flows into the left-hand end of the cylinder 74 through the central passage 76 in the control piston. The pressure on opposite sides of the control piston 53 is thereby equalized and the latter is moved to its left-hand position by the action of its spring 78.

This left-hand movement of the control piston shifts the slide valve St to its left-hand or return position of FIG. 3. In this position of the slide valve, pressure air may flow from the valve chamber 4S through the opening 32 in the valve plate 38, passage 28, into the lower end of the main pneumatic cylinder 22, The main pneumatic piston 24 yand power piston 90 are thus moved to their normal upper position of FIG. l. During this upward or return stroke of the pneumatic pist-on, the air in the pneumatic cylinder 22 above the pneumatic piston 24 exhausts to atmosphere through the passage 26, slide valve t?, exhaust passage 62, and muffler packing 64.

Air pressure in the control valve passage 80 holds the control valve 82 in its closed position of FIG. 1 to retain the parts of the gun in their normal positions of FIG. 1. When the control valve S2 is depressed, air leaks from the pass-age 80 to atmosphere through the leakage space 35 between the control valve stem S4 and its bore S6. Pressure of the air in the right-hand end of the control piston cylinder 74 is thereby reduced. The high pressure air in the left-hand end of the cylinder 74 moves the control piston 58 -to its right-hand position of FIG. 4. The slide valve Si) is thereby shifted to its right-hand position of FIG. 4.

Pressure air now flows from the valve chamber 48 through the opening 30' in the valve plate 3S, passage 26, to the upper end of the pneumatic cylinder 22 to cause downward movement of the main pneumatic piston 24. The air in the pneumatic cylinder 22 below the piston 24 exhausts to atmosphere through the passage 2S, slide valve 50, and exhaust passage 62.

Upon downward movement of the power piston rod 89 with the pneumatic piston 24, the conical v-alve face 112 of the power pistonv rod shoulder 108 engages the valve `seat 114 on the power piston 90 to effectively seal the power piston to the power piston rod.

The hydraulic fluid displaced from the power cylinder space 116 below the power piston, during the downward pumping stroke of the latter with the pneumatic piston 24, flows through the passage 120 into the right end of the head cylinder 122. This fluid acts on the right-hand side of the head piston 138 to move the latter in its lefthand pulling stroke. Because of the large area of the pneumatic piston 24, as compared with the area of the power piston 90, the pressure of the hydraulic fluid acting on the head piston 13S will be appreciably greater than than the air pressure acting on the pneumatic piston.

During the down stroke of the power piston, the sealing faces 266 and 208 on the power piston rod 89 and return piston 196, respectively, separate to open restricted passageway 211. The resulting left-hand movement of the head piston 138 displaces hydraulic liuid from the left-hand end of the head cylinder 122 into the upper end of the return cylinder 190 and the interior of the return piston 196. Upon downward movement of the return piston 196 being terminated by engagement of the latter with the stop ring 204, the restricted passageway 211 is enlarged due to the end of the rod 210` being completely withdrawn from opening 201. Fill-in hyvdraulic fluid now ows freely from the reservoir 132 through the now open passage 201 in the lower end of the return piston 196.

When the head piston 138 reaches the left limit of its left-hand pulling stroke against the stop sleeve 136, at which time the fastener will have been set and swaged, the control valve S2 is released. The air pressure in the control Valve passage 89 then moves the control valve to its closed position.

Closure of the control valve 82 permits the air pressure across the control piston 5d to again equalize. The control piston is then shifted to the left by the action of its spring 7S to move the slide valve 50 from its righthand position or" FIG. 4, to its left-hand return position Of FIG. 3.

As previously described, this action communicates the valve chamber 48 with the lower end of the pneumatic cylinder 22 to cause the return stroke of the main pneumatic piston 24 and power piston rod 89. During the upward return stroke of the power piston rod S9, the valve seat 112 on the piston rod shoulder 108 separates from the valve seat 114 on the power piston 90. This permits hydraulic fluid in the power cylinder 92 to leak past the power piston during its upward movement in the power cylinder.

Near the upper end of the return stroke of the power piston rod 89, the sealing faces 206 and 20S of the piston rod shoulder 168 and return piston 196, respectively, engage to close the escape passage 211 in the lower end of the return piston. During subsequent upward movement of the return piston with the power piston rod 89, the hydraulic fluid trapped above the return piston is forced into the head cylinder 122 to the left of the head piston 138. The head piston is thereby moved in its right-hand return stroke to release the swaging anvil on the pulling head from the swaged collar of the fastener and return the draw bolt of the pulling head to its normal position in readiness for another setting operation` Upon the head piston 13S reaching -the right-hand limit of its return stroke, the excess fluid trapped above the return piston 196 ows through the by-pass passage 214 and check valve 216 back to the reservoir 132.

It is eviden-t from the preceding description that the power piston, return piston, yand their respective cylinders form, in elfect, a double-acting, hydraulic lluid pump which, on one stroke, supplies hydraulic iiuid under pressure to one side of the work piston 138 to move the latter in one direction and, on the other stroke, supplies hydrauiic fluid under pressure to the other side of the work piston to move the latter in the opposite direction. The check valve means of the power piston and the return piston act to replenish the supplyv of hydraulic fluid in each end of this double-acting, hydraulic fluid pump during its strokes.

It will be apparent, therefore, that there has been described and illustrated a pneumatic hydraulic gun which is fully capable of attaining the objects and advantages preliminarily set forth.

While the preferred embodiment ofthe invention has been disclosed for illustrative purposes, numerous modilications in design and arrangement of parts are obviously possible within the scope of the following claims.

I claim:

l. In a lluid powered gun for setting rivets, the combination of a handle having a first cylinder, a work piston movable in said cylinder including a piston rod extending through one end of the cylinder to the exterior of said handle, a hydraulic fluid reservoir in said handle, said handle having a second cylinder opening at one end to said reservoir and communicating at its other end to said one end of the rst cylinder, power piston means movable in said second cylinder, said power piston means including one-way check valve means which open upon movement of said piston means toward said one end of the second cylinder to permit flow of hydraulic iiuid past said piston means to said other end of the second cylinder, movement of said piston means toward the other end of said second cylinder closing said check valve means whereby hydraulic fluid is pumped from said second cylinder to said first cylinder to move said work piston in one direction, a third cylinder in said handle opening at one end to said reservoir and communicating at its other end with the other end of said first cylinder, a return piston movable in said third cylinder, said return piston having 4a passage opening through opposite sides thereof, cooperating engageable means on said power piston means and return piston for moving the latter `toward said other end of the third cylinder and closing said passage during movement of said power piston means toward said one end of the second cylinder whereby to pump hydraulic fiuid Ifrom said third cylinder to said first cylinder for moving said work piston in the opposite direction, said cooperating means disengaging to open said passage lduring movement of said power piston mean-s toward said other end of the second cylinder to permit lill-in hydraulic fluid to fiow from the reservoir, through said passage, to said other end of the third cylinder, means yfor moving said return piston toward said one end of the third cylinder during said latter movement of the power piston means, and means for moving said power piston means in opposite directions.

2. The subject matter of claim 1 wherein said second and third cylinders are coaxial and have said ends thereof opening toward one another, said cooperating means including `a Valve seat on said return piston about said passage, and a valve face on said power piston means engageable with said valve seat.

3. The subject matter of claim 1 wherein said power piston means comprises a power piston rod, a floating power piston capable of limited axial movement on said power piston rod, there being a passage between said power piston and rod, and said check Valve means comprises a valve seat on said power piston about said passage and a valve face on said power piston rod engageable with said valve seat to close said passage upon movement of said power piston rod toward said other end of the second cylinder.

4. A fluid powered gun for setting rivets comprising an elongate handle having a first transverse cylinder lat one end, a work piston movable in said cylinder including a piston rod extending through one end of said cylinder to the outside of said handle, `a hydraulic Huid reservoir in said handle, second and third coaxial, longitudinally extending cylinders in said handle having -facing open ends opening to said reservoir, there being passages in said handle communicating the other end of Said second cylinder to the other end of said rst cylinder and the other end of said third cylinder to said one end of the first cylinder, a return piston movable in said second cylinder, there being a passage opening through opposite sides of the return piston, yieldable means biasing said return piston toward said one end of the second cylinder, the other end of said handle having a fourth main cylinder coaxial with and larger than said second and third cylinders, a main piston movable in said main cylinder, a power piston rod secured to said main piston and extending into said other end of said third cylinder, means slideably sealing said power piston rod to said handle between said `third and fourth cylinders, means for selectively admitting pressure fluid to and venting opposite sides of said main piston, a floating power piston on said power piston rod movable in said third cylinder, means connecting said power piston rod and power piston for limited relative axial move-ment thereof, there being a passage between said power piston and rod, cooperating one-way check valve means on said power piston and power piston rod for closing the latter passage upon movement of the power piston rod toward said other end or the third cylinder, said check valve means opening upon movement of the power piston rod in the opposite direction, and cooperating -means on said power piston rod and return piston for closing the passage through the latter piston and moving the return piston toward said other end of the second cylinder during movement of said power piston rod in said opposite direction.

5. The subjec-t matter of claim 4 wherein said return piston has a greater displacement than said work piston, there being a passage communicating said other end of the first cylinder to said reservoir, and one-way check and relief valve means in said latter passage arranged to open to permit iiow of hydraulic uid from said first cylinder to said reservoir upon the pressure of fluid in said other end of the first cylinder reaching a predetermined value.

6. In a tuid powered gun `for setting rivets, a handle having a first cylinder, a work piston movable in said cylinder including a piston rod extending to the exterior of the handle, a hydraulic Huid reservoir in said handle, a second cylinder in said handle communicating at one end to one end of said first cylinder, a return piston movable in said second cylinder toward said one end of the latter cylinder to pump hydraulic fluid from said second cylinder to said first cylinder for moving said work piston in one direction, means for communicating said one end of the second cyl-inder to said reservoir during movement of said return piston toward the other end of the second cylinder, said return piston having a greater displacement than said work piston, there being a passage communieating said one end of the firsty cylinder to said reservoir, one-Way check and relief valve means in said passage which opens to permit flow of hydraulic fin-id from said rst cylinder to said reservoir upon the pressure of the 4fluid in said one end of the first cylinder attaining a predetermined Value, reciprocating power means for moving said return piston toward said one end of its cylinder on each stroke of the power means in one direction, means for returning the return piston toward the other end of its cylinder on each stroke of the power means in the opposite direction,'and means operated by ,said power means for pumping hydraulic fiuid from said reservoir to the other end of lche first cylinder `during each stroke of the power means in said opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 

